Ethiopia comprises of millions of farm households who are resource-poor, and food-insecure due to declining crop productivity and vulnerability to climate change. The “Trees for food security” project supports innovative research on the use of agroforestry systems to raise crop yields, enhance livelihoods and improve environmental outcomes. We hypothesized that thorough characterization of target sites and trying out appropriate options in participatory trials is critical in informing agroforestry options for adoption by farmers. A socio-economic baseline was carried out in two contrasting agro-ecological areas of semi-arid East Showa zone and sub humid East Welega / West Showa zones of Oromia regional state in Ethiopia. Respondents from over 300 households for each site, drawn from five and four districts in semi-arid and sub humid areas respectively, were interviewed using a structured questionnaire. Issues captured were to establish the relationships between food security, tree and crop data, health and nutrition, and income. Two planting niches (farmlands and homesteads) were selected for establishing participatory agroforestry trials within each area. Treatments in the trials included; the effectiveness of different seedling protection mechanisms in improving seedling survival; the effect of soil moisture retention mechanisms in five drier sites and manure application in three moister sites around homesteads. Trees and shrubs planted in the trials include Cordia africana, Croton macrostachyus, Grevillea robusta and Moringa stenopetala on farmlands and homesteads, Faidherbia albida, Sesbania sesban, Leucaena leucocephala and Cajanus cajan on farmlands, Mangifera indica and Persea americana in homesteads. Results show higher tree abundance and diversity in the sub-humid area than the semi-arid area. The five most frequent reasons why farmers planted trees in both sites were mainly for firewood, income, shade, live fence and timber. The preferred niches were home compound, scattered in fields and live fences. Planting trees and shrubs in crop fields in a patterned fashion is a new experience for the farmers in the project sites. Participatory approaches involving farmers, extension agents and researchers in the research process is well embedded in the national program that makes it instrumental to scale up the use of trees within farming systems. Results from baselines and participatory trials will then be used to identify scaling domains for agroforestry options not only in Ethiopia but also in similar agro-ecological areas of Uganda and Burundi.