ABSTRACT Vegetable as a group of crops from the horticulture category has a very wide significance both as a source of food and income. The objective of this research thesis was, to identify market channels and the role of actors, to analyze the determinants of vegetable market supply, its constraints, and opportunities for potato and onion production and marketing. The findings indicate that potato and onion market chain actors identified in the study area include producers, rural collectors, brokers, retailers, wholesalers and consumers. Producers were price takers and hardly bargain the price due to fear of post-harvest losses, in case the product was not sold. The primary data was generated by household survey using a pretested structured questionnaire and key informant interview using checklists. The data collected from 150 smallholder farmers, 70 traders, and 15 consumers. Five market channels were identified for potato and onion respectively. The highest gross marketing margins of producers in potato and onion markets were 65.76% and 72.84% in channels III and V, respectively. The ordinary least square regression model results showed that seven variables such as productivity of potatoes, off/non-farm income and area of land allocated for potato and family size, education, and irrigation access significantly and positively affect the volume of potato supplied to the market while age of household significantly and negatively determining the quantity of potato supplied to the market. Moreover, the number of onions supplied to the market was significantly and positively affected by the yield of onions produced per hectare, educational level of household, access to market information, farming experience, last year's price, and area of land allocated for onion while the distance to the market significantly and negatively determining the quantity of onion supplied to the market. Based on the results, the study recommended that they need to improve the input supply system, improve farmers’ knowledge and experience on vegetable production, inspire market information, improve productivity and volume sales of vegetables, strengthen the linkage/interaction among vegetable market chain actors, expanding the accessibility of market infrastructure development.