In 2004, Algarve was the first region of the country to be declared a GMO-free zone. Sixteen municipalities in the region are part of the zone. The campaign was organized by the Associação de Municípios do Algarve (AMAL, or the Association of Municipalities of the Algarve region).

In 2005, another law was adopted to allow genetically modified varieties to coexist with conventional crops and the production of organic food. Several groups question this coexistence because of the risk of cross-contamination.

It was only in 2007 that a decree authorizing the creation of GMO-free zones by farmers' decisions or a municipal initiative was issued. The decree stipulates, however, that the decision to establish a GMO-free zone must be approved by an absolute majority of the members present at a local municipal assembly. While these decisions are not binding, but they are an important tool for fighting GMOs.

In 2007, the existence of a plantation of genetically modified corn grown by Monsanto in Herdade da Lameira, Silves, in the Algarve region was denounced. AMAL and the Association for the Defense of the Cultural and Environmental Heritage of Algarve (ALMARGEM) took a stance against this kind of crop. On August 17, 2007, about 150 people from the Movimento Verde Eufémia travelled to Herdade da Lameira to protest and destroyed the GMO cornfield of approximately 50 hectares. A representative of the Bloco de Esquerda (BE, Left Block party) and environmental associations voiced their support for the action, declaring that even though they do not agree with the Movement Verde Eufémia's tactics, they recognized the need to discuss and resist GMOs in Portugal. Even though the action was criticized and criminalized by the national press, it did help highlight the need to discuss the issue of GMOs in the country.

The No GMOs Coalition has been working on this issue since 1999. It is composed of associations and environmental groups. Its actions include activist workshops, protests, participation in the public consultations and meetings, publicly questioning government actions and decisions, organizing information sessions, lectures, conferences, awareness campaigns and debates with the population and the public administration, the dissemination of research results, interventions in schools and universities, and communicating with farmers, supermarkets and consumers that produce and consume GMOs, etc. In 2013, for example, it organized a visit to the ten largest Portuguese hypermarkets in the cities of Lisbon and Porto to assess the supply of food products containing GMOs and the information available to consumers.

In Portugal, the main actions related to the production, import and consumption of GMOs are: activities to combat the spread of GMO corn plantations and provide information on these crops; boycotts of GMO foods; support for the "free seeds" campaign in coordination with the broader European movement; opposition to transnational corporations’ monopoly over seeds; fight against and warn people about the use of herbicides in public places and the increasing use of herbicides containing glyphosate.

Several municipalities in the Algarve region and another 27 municipalities in Europe were declared GMO-free zones in 2011. In 2012, the islands of Madeira and Azores also declared themselves GMO-free zones.

In 2015, data on GMO plantations in Portugal in 2014 showed that Algarve (an official GMO-free zone) is the region in the country with the smallest area of land used to grow GMOs, whereas Alentejo has the biggest.

Concerned with the increase in the use of glyphosate in Portugal, in March 2014, environmental organizations and the No GMO Coalition sent a letter to all mayors in the country to warn them of the risks of the use of herbicides in urban spaces to the environment and health.

Tests carried out in April 2016 by the No GMO Coalition in collaboration with the Detox Project found high levels of glyphosate in the urine of 26 Portuguese volunteers and some food samples.

On December 27, 2017, the European Commission renewed the license of glyphosate for a five-year period after a scientific study concluded that there was no connection between glyphosate and cancer. The measure was approved by 18 EU member states; Portugal abstained from the vote.

– In 2007: 4199 ha of MON 810 out of a total of 116 700 ha of maize 3.6%

– In 2008: 15% increase to 4839 ha