The Rio is a Steamboat and Colorado mainstay. I think the Big Tex is one of the best margs in town. Their food is consistently good. My favorites are the chile relleno and vegetarian tostada. The restaurant has a very upbeat and fun atmosphere and great roof top seating. Plan to arrive before peak dinner hours on Friday and Saturday nights and during the summer.
The Rio Grande is a great lunch and dinner tex-mex restaurant in central downtown Steamboat. Their margarita's will make your head swim, and they only allow you to have 3, more than that will make you loco. They have great fajitas and the complimentary chips and salsa are really good. Most of their menu is truly tasty. The atmosphere is warm and cheerful. The staff is friendly and efficient. A great place for food and fun.