Few web-based experiments have explored spoken language production, perhaps due to concerns of data quality, especially for measuring onset latencies. The present study highlights how speech production research can be done outside of the laboratory by measuring utterance durations and speech fluency in a multiple-object naming task when examining two effects related to lexical selection: semantic context and name agreement. A web-based modified blocked-cyclic naming paradigm was created, in which participants named a total of sixteen simultaneously presented pictures on each trial. The pictures were either four tokens from the same semantic category (homogeneous context), or four tokens from different semantic categories (heterogeneous context). Name agreement of the pictures was varied orthogonally (high, low). In addition to onset latency, five dependent variables were measured to index naming performance: accuracy, utterance duration, total pause time, the number of chunks (word groups pronounced without intervening pauses), and first chunk length. Bayesian analyses showed effects of semantic context and name agreement for some of the dependent measures, but no interaction. We discuss the methodological implications of the current study and make best practice recommendations for spoken language production research in an online environment.